This trio of cowl patterns are so simple they hardly qualify as patterns, and you can adapt them however you like. Like a larger circumference? Increase the cast-on count by 150% or 200%. Like a narrower or deeper cowl? Knit fewer or more rows accordingly. Want something drapier? Use a finer yarn and increase the cast-on count to compensate. All that really matters is the stitch multiple for the repeat, which is noted with each pattern.

You could use anywhere from a size 15 needle up, depending how jumbo you want your stitches to be. Gauge isn’t terribly important here.